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Wet-bulb temperature

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Re: Wet-bulb temperature

#171

Post by gorbypark »

josiahpeters wrote: post #169
sokoloff wrote: post #143

Earlier quoted context omitted.

I’ve occasionally wanted to try snowmaking at home on brutally cold days. Any tips for someone wanting to try this at home? Let’s assume that I have access to tap water at 60psi dynamic pressure and air at 90psi and 10 SCFM continuous (more for short bursts if needed).

I did this exact thing this past winter. I spent about $100 on pipe fittings and purchased an external mixer DIY nozzle set from here: https://www.snowathome.com/our_products/SG3_e-type_nozzle_ki... I made snow in my front yard a few times. I also completely covered my tree and car in a blanket of ice a few times too. It was a fun little project to hack on.

That's pretty cool that they are selling "external mix" plans/kits. Snowmaking (at scale) is incredibly energy intensive and over the last few years many resorts have been moving towards various "low-energy" gun designs, which basically means external mix.

They definitely don't make as good snow at marginal temperatures but it's impressive what they can do given a lot use 1/20th of the compressed air compared to a tradition air/water snowgun.

A tradition air/water gun is just an 1.5" air inlet, a 1.5" water inlet, a mixing chamber and a nozzle. At higher temperatures, they take an incredible amount of air. We had a few guns that could take 300 horsepower worth of an air compressor, each, to run at -2.5 celsius wet bulb. As is gets colder it gets a little more efficient.

There are some designs that are basically the same but incorporate a "baffle" that attempts to cut down the size of the mixing chamber when there's a high air/water mixture to make them more efficient, but those baffles would often get stuck open, making them useless.

A fangun is the style of snowgun that uses a giant electric fan to project the snow out from the gun. There is an onboard electric air compressor hooked up to a few nozzles that spray out a mixture of air and water. The tiny droplets freeze into the "nucleus" (a tiny ice particle), which other droplets from water-only nozzles bind onto and freeze, creating a "snowflake".

An external mix gun is basically a fangun, minus the big electric fan, and suspended 30+ feet in the air on a pole. A small number of nozzles spray out an air/water mix, creating the nucleus, and then water only nozzles spray out droplets that then bind to the nucleus. It works but needs to be a bit colder, and they are much more susceptible to winds (especially cross winds). If winds don't allow the two types of sprays to mix, you get a nice skating rink instead of snow!

Re: Wet-bulb temperature

#172

Post by hoseja »

ch4s3 wrote: post #85
allemagne wrote: post #57

Earlier quoted context omitted.

There was about paragraph or so spent on that realistic response, and then huge swathes dedicated to India switching to collectivized farming (a la early Soviet Union), the world's central banks putting carbon offsets onto a blockchain, and millions of Americans willingly displacing themselves to create a giant wildlife preserve in the midwest.

KSR is sliding in the direction of outright promotion of eco-fascism and I can't say it makes for good literature.

I've definitively soured on him after that dolphin chapter.

Re: Wet-bulb temperature

#173

Post by herbstein »

JeremyNT wrote: post #120
bradford wrote: post #89

Maybe this is a pet peeve of mine, but I'm annoyed with the use of the term 'wet bulb event' here and elsewhere. Wouldn't it put less burden on the reader to just say "wet bulb 35C"? (That is the temperature that most people seem to be referring to when they say 'wet bulb event'.) Every place on earth has a wet bulb temperature, all of the time. Saying "wet-bulb event" doesn't really help explain the web-bulb tempera…

I feel like the terms in use around this are quite abstract and hard to reason about. I like that the wikipedia article converts this to something more useful to intuit for most of us: > Even heat-adapted people cannot carry out normal outdoor activities past a wet-bulb temperature of 32 °C (90 °F), equivalent to a heat index of 55 °C (131 °F). A reading of 35 °C (95 °F) – equivalent to a heat index of 71 °C (160 °F)…

> and six hours is a long time to be exposed to the elements even at the current levels of heat.

In the air-conditioned US. Much of the world gets as hot, if not hotter, without AC to help alleviate the heat.

Re: Wet-bulb temperature

#174

Post by makeitdouble »

jcranmer wrote: post #99
makeitdouble wrote: post #6

Earlier quoted context omitted.

I assume parent means a period of time where the ambient temperature is at or above the wet bulb temperature.

Ambient temperature is always at or above the wet-bulb temperature, by definition. A wet-bulb temperature measures the temperature that can be achieved after energy loss due to evaporation of water, so as long as evaporation is possible (humidity < 100%), it is lower than the actual temperature.

Thanks for the correction, I need to revisit the subject in full I think.

Re: Wet-bulb temperature

#175

Post by alangibson »

jabradoodle wrote: post #138
alangibson wrote: post #133

Earlier quoted context omitted.

Another post demonstrating my point. 35K people in the US alone die in traffic every year. We have normalized this figure (see your response) as we will normalize climate deaths. What I would do about traffic deaths is irrelevant to my point.

I find your approach arrogant; of course I understand that people die in car crashes and yet we continue to use them. Your original point was: >Yet there is zero momentum toward doing anything about those from a policy standpoint. This is clearly false. There are many effective regulations and travelling by car continues to get safer. Yes people still die, yes we already somewhat normalise people dying from e.g. air…

I should have written "fixing the problem" instead of "doing anything about those" as I did in other comments. I define "fixed" as reaching and sustaining the lower bound. So basically excluding deaths due to act of god only.

> There are people who do think about these things every day. There are people who dedicate life to working on problems and progress is being made.

Exactly. Despite that, here we are with 35K traffic deaths a year. Here's what would actually be necessary to "fix" the problem:

- 20 year project to build a tremendous amount of passenger rail - Manhattan project for self-driving cars - 10 year project to upgrade all city and highway signage to be self-driving car friendly - Close roads to human-driven cars when self-driving upgrades are ready

This probably sounds crazy to you. It sounds crazy to me too. And that's why I'm blackpilled on climate change: if we can't and won't do what it takes to fix traffic or gun fatalities on a national level, we definitely won't do it for a problem several orders of magnitude more difficult on a global level.

> Saying that a major event would have no impact on the zeitgiest is questionable given history.

There will be an impact. Just most likely not a positive one. It could highly negative (see post-9/11 wars), or completely insufficient (our current response to climate change).

Re: Wet-bulb temperature

#176

Post by LeifCarrotson »

abeppu wrote: post #159
LeifCarrotson wrote: post #88

Earlier quoted context omitted.

The ways in which we fail to address societal issues are not in fact our responsibility, they're a systemic issue that is a function of human nature - or political nature/societal nature - that will not be solved by morose feelings of condemnation. "Why can't people not be the way they are" is just as useless a sentiment as "Why can't mathematics not be the way it is", and will be just as ineffective at causing 2 and…

To me this response just seems incoherent. > The ways in which we fail to address societal issues are not in fact our responsibility, they're a systemic issue that is a function of human nature ... - that will not be solved by morose feelings of condemnation. Are we not society? Do we not make up the system? But more importantly, you're refuting a statement of responsibility by saying the underlying problem won't be…

An individual can be expected to be moral, and should be judged if they are not.

A population or corporation should be expected to be moral. Collective behaviors are a function of incentives and penalties, of pure economics.

If your plan to fix the problems in society relies on every member selflessly cooperating and fails if one member defects, if you create a system that is trivially exploited by rich amoral sociopaths behaving like rich amoral sociopaths, then the defector is morally to blame when it fails, but that's still the expected outcome.

Re: Wet-bulb temperature

#177

Post by jncfhnb »

sokoloff wrote: post #156
jncfhnb wrote: post #150

Earlier quoted context omitted.

You just put your feet in the water and transfer heat to the water. It would not heat up to 35 in no time.

1 BTU is the amount of energy required to raise 1 pound of water by 1°F. Take 5 gallons (~42 pounds) at say 70°F (21°C). Raising that 42 pounds of water by 25°F/14°C will take just over 1K BTU. That's maybe 2 hours of cooling per person and it's not at all obvious that during such a heat event that you'll have access to a continued source of 70°F/21°C water. If you only have access to 82°F/28°C water, 5 gallons only…

So let’s use your logic and ask how long could a person survive in a sauna?

Re: Wet-bulb temperature

#178

Post by [deleted] »

jncfhnb wrote: post #177
sokoloff wrote: post #156

Earlier quoted context omitted.

1 BTU is the amount of energy required to raise 1 pound of water by 1°F. Take 5 gallons (~42 pounds) at say 70°F (21°C). Raising that 42 pounds of water by 25°F/14°C will take just over 1K BTU. That's maybe 2 hours of cooling per person and it's not at all obvious that during such a heat event that you'll have access to a continued source of 70°F/21°C water. If you only have access to 82°F/28°C water, 5 gallons only…

So let’s use your logic and ask how long could a person survive in a sauna?

[deleted]

Re: Wet-bulb temperature

#179

Post by IKantRead »

mensetmanusman wrote: post #157
IKantRead wrote: post #39

Earlier quoted context omitted.

Or the million+ deaths in the US from Covid, which I have seen brushed off on HN as not a big deal. It's remarkably how quickly people incorporate tragedy as normal when it doesn't fit their worldview. If you travel to 2000 and told people "in 2020 a pandemic will kill over 1 million Americans, and a good portion will brush it off as a 'nothing burger'" people would think you were being ridiculous and would dismiss i…

There are a million HIV deaths annually. Once something becomes endemic we accept it as a new mode of existence. A million people die a week, worldwide, from all causes.

In the US, which is the region I'm citing for covid deaths, HIV causes ~20,000 deaths a year [0].

Last I checked people are quite considered with global HIV death, especially since they can obviously be reduced dramatically.

0. https://www.hiv.gov/hiv-basics/overview/data-and-trends/stat...

Re: Wet-bulb temperature

#180

Post by ch4s3 »

hoseja wrote: post #172
ch4s3 wrote: post #85

Earlier quoted context omitted.

KSR is sliding in the direction of outright promotion of eco-fascism and I can't say it makes for good literature.

I've definitively soured on him after that dolphin chapter.

I can't find that part now, but there's plenty of really rotten stuff in the book.
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